The Long Term Evolution (LTE) telecommunication system is an evolution of the Wideband Code Division Multiple Access (WCDMA) telecommunication system, introducing a new air interface. LTE has many attractive properties that can be used for future development of telecommunication services. A specific technical challenge in e.g. LTE and similar systems is the scheduling of uplink channels to time intervals and frequencies where the interference conditions are favourable, and where there exist a sufficient capacity in the uplink. This can be done since in LTE, different users are allocated to different sub-bands (also called tones) during each timeslot. Due to leakage between sub-bands, other existing users of the cell all contribute to the interference level of a specific user in the uplink of LTE systems. Further, terminals in neighbour cells also contribute to the same interference level. This is because all users and common channels of a all cells transmit in the same uplink frequency band when LTE technology is used. The users of neighbor cells that transmit on the same tones as users in the own cell will hence produce interference. Hence two sources of interference is present—from users in the own cell and from users of neighbor cells.
In order to schedule the traffic in the own and neighbor cells efficiently, it is desirable to know the level of interference for each tone of the uplink. With such knowledge it becomes possible to schedule traffic to free tones where the interference level is low. In that way the transmission from the terminal (UE) to the base station (eNode B) will be efficient. Reversing the argumentation, it is also clear that scheduling to tones with a high interference level should be avoided, the reason being that such a scheduling would interfere ongoing uplink transmission in neighbor cells.
As discussed above, the interference power at a specific tone is the sum of the interference from neighbor cells and the leakage power from the other tones of the own cell. Now, the leakage from other tones of the own cell depends in a known way on the selected filter bank. Hence, knowledge of the total power levels of the received signals of the uplink of the own cell can be used to compute the expected leakage power, that affects a specific tone. The consequence is that it is possible to filter out the own cell interference, at least to some extent. That would leave the neighbor cell interference as the major source of interference, for each tone of the own cell.
The interference level of a specific tone of a cell in e.g. an LTE system is usually expressed with respect to some reference, typically the thermal noise power floor. Consequently, the noise power floor, have to be determined, in order to determine the interference level. Determinations of noise floor have in the past typically been associated with relatively large uncertainties, often of a size of several dBs. This is an effect of unknown scale factor errors of the front end receiver electronics. Recently, means for estimation of the noise floor have been disclosed in patent applications PCT/SE2005/001242 and PCT/SE2006/050242. These applications describe means for noise floor estimation that are suitable for code division multiple access communications systems. They do, however, not disclose any means suitable for estimation of the noise floor for single tones of the LTE uplink. Neither do they address the filtering of leakage between tones of the own cell, that is a consequence of the uplink multiple access method used in LTE, which is different from the one in code division multiple access. Finally, they do not address the estimation of the neighbor interference level of specific tones of the LTE uplink, exploiting a (possibly uncertain) estimate of the thermal noise power floor of said specific tones, Therefore, there is a need for methods and arrangements for providing efficient and accurate real time estimates of the thermal noise power floor and the neighbor cell interference level, applicable to the LTE uplink multiple access method.
The admission of new users into the LTE telecommunication system provides a way to regulate the load of LTE cells. This admission may be performed in either the eNode Bs or in another node. The admission rules may typically use information on the total power level of the cell, the own channel power of the cell, the neighbor cell interference level of the cell, as well as information on the thermal noise power floor of the cell. Therefore there is a need for methods and arrangements for aggregating the total power, own channel power and neighbor cell interference power, of each of the subsets of frequency sub-bands of the total LTE frequency band, to obtain the total cell power, the total own cell channel power and the total neighbor cell interference level. Furthermore, there is a need for means providing signaling of a subset of the total cell power, the total own cell channel power, the total neighbor cell interference level and the thermal noise floor measure to an external node, or another function within the e Node B.